public class MyLinkedList {
    ListLode head;
    ListLode last;
    static class ListLode{
        ListLode prev;
        ListLode next;
        int val;

        public ListLode(ListLode prev, ListLode next, int val) {
            this.prev = prev;
            this.next = next;
            this.val = val;
        }
    }
    //头插法
    public void addFirst(int data){
        ListLode node=new ListLode(null,null,data);
        if(head==null){
            head=last=node;
            return;
        }
        node.next=head;
        head.prev=node;
        head=node;
    }
    //尾插法
    public void addLast(int data){
        ListLode node=new ListLode(null,null,data);
        if(head==null){
            head=last=node;
            return;
        }
        last.next=node;
        node.prev=last;
        last=node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index<0||index>size()){
            System.out.println("index out of bounds error");
        }
        if(index==0){
            addFirst(data);
        }else if(index==size()){
            addLast(data);
        }else{
            ListLode cur=searchNodeByIndex(index);
            ListLode node=new ListLode(null,null,data);
            node.next=cur;
            node.prev=cur.prev;
            cur.prev.next=node;
            cur.prev=node;
        }

    }

    private ListLode searchNodeByIndex(int index){
        ListLode cur=head;
        while(index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListLode cur = head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListLode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head==null){
                        head=last=null;
                    }
                    head.prev = null;
                    return;
                }
                if(cur==last){
                    last=last.prev;
                    last.next=null;
                    return;
                }
                cur.next.prev=cur.prev;
                cur.prev.next=cur.next;
                return;
            }
            cur=cur.next;
        }
        System.out.println("没有要删除的元素");
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListLode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head==null){
                        head=last=null;
                        cur=cur.next;
                        continue;
                    }
                    head.prev = null;
                    cur=cur.next;
                    continue;
                }
                if(cur==last){
                    last=last.prev;
                    last.next=null;
                    cur=cur.next;
                    continue;
                }
                cur.next.prev=cur.prev;
                cur.prev.next=cur.next;
                cur=cur.next;
                continue;
            }
            cur=cur.next;
        }
        System.out.println("没有要删除的元素");
    }
    //得到单链表的长度
    public int size(){
        ListLode cur=head;
        int count=0;
        while(cur!=null){
            count++;
            cur=cur.next;
        }
        return count;
    }
    public void display(){
        ListLode cur=head;
        while(cur!=null){
            System.out.println(cur.val);
            cur=cur.next;
        }
    }
    public void clear(){
        ListLode cur=head;
        while(cur!=null){
            ListLode curN=cur.next;
            cur.next=null;
            cur.prev=null;
            cur=curN;
        }
        head=last=null;
    }

}
